Screw-cutting lathe



F. H. DANIELS.

SCREW CUTTING LATHE. APPLICATION FILED JULY 12. 1919.

Patented Mar. 15, 1921.

Z SHEETSSHEET I.

UNITED STATES PATENT OFFICE.

FRANK H. DANIELS, OF PHILADELPHIA, PENNSYLVANIA, ASSIGN OR TO THE JOHN M.

ROGERS WORKS, INC., 01 GLOUCESTER CITY,

NEW JERSEY.

NEW JERSEY, A CORPORATION OF SCREW-CUTTING LATHE.

Specification of Letters Patent.

Patented Mar. 15, 1921.

Application filed July 12, 1919. Serial No. 310,462.

T 0 all to ham it may concern:

Be it known that I,.FRANK H. DANIELS, a citizen of the United States, residing at Philadelphia, county of Philadelphia, and State of Pennsylvania, have invented a new and useful Improvement in ScrewGutting Lathes, of which the following is a full, clear, and exact description, reference being had to the accompanying drawings, which form a part of this specification.

My invention relates to an attachment for lathes, thread grinders, or thread milling machines, in connection with their use in cutting threads.

I have found thatin cutting threads where great accuracy is essential, as in screws used 1n the construction of delicate instruments and gages, the present methods are deficient because of the presence of lost motion in the feed screw, gears, etc., which results in variations inthe pitch of the screw The object of my invention is to provide an attachment for lathes, which will permit threads to be cut with the greatest accuracy and which will permit of the production of screws with uniformly accurate pitch.

I will now describe my invention in detail in connection with the accompanying drawings in which like symbolsrefer to like parts in the various figures.

Figure 1 is a side elevation of a lathe with the device involving my invention attached.

Fig. 2 is a side elevation of the device 1nvolving my invention.

Fig. 3 is an end view of the subject of Fig. 2.

Fi 4 is a horizontal section along line H Fig. 2. I

Figs. 5, 6 and 7 are views of details of the device involving my invention.

Upon the bed a are mounted the head and tail stock centers 6. A. tool support 0 1s mounted on a carriage 03 adapted to travel horizontally on the ways 6, in the bed, under the influence of the right hand threaded feed screw 7. The usual power driven speed pulleys and various gears are provided to drive the work and the feed screw, but I do not show them, as they conform to the usual des1 n.

A sleeve 9 provided with a flange at one end is passed over the feed screw and bolted to the carriage c, the flange g taking the place of the usual feed nut. A second sleeve it having a yoke i at one end is passed over the feed screw and fitted into the end of sleeve 9 and positioned by a screw j. two sleeves are fastened of bolts is. A casing Z is 0. adjacent to the yoke by a bolt m and lug n. Within and pivoted on bolt 0 to the easlng is a block 19 in which is formed a cylindrical guideway Set screws 1' extend through slots 8 in the casing and engage the block. A nut t, in engagement with the feed screw and embraced by yoke h is connected to a short slide a adapted to travel in the guldeway g by means of a pin o which may be lntegral, with the nut or connected to it as shown in the drawing Fig. 7.

It will be noted that the pin 2) permits the block u to turn about its own axis and the nut 25 to move toward and away from the block, as is necessitated by its movement in guldeway g. In operation, if it is found that the lathe 1s not cutting a screw with an accurate pitch, it 1s first determined whether the error is in more than exactly the required number of turns to the unit, or less. Then the set screws r are loosened and the block p turned so that one end is slightly higher than the other. If the error is minus, the inner end is raised, and if plus the outer end is raised. The set screws 7* are tightened up to clamp the block in position.

If the error is minus, the inner end of the block is raised, putting the guideway g on afslant. As the feed screw turns, the nut travels forwardly along the screw andcauses the slide a to travel along the guideway. Since the guideway presents an upward incline, in the direction of travel of the slide, as the slide travels up the incline it turns the nut on the feed screw in a direction contrary to the thread of the screw and causes the carriage to travel faster relatively to the speed of rotation of the screw than the lathe is geared up for.

The tool is made to travel by the nut, through its bearing against yoke i and the sleeves g and h, which, as described, are connected together, sleeve 9 being connected to the carriage.

As the nut travels faster than if it had no turning movement, it is obvious that the tool will travel proportionately faster and the minus error can be made to disappear.

If the error is plus. the outer end of the block is raised and the guideway q will together by means clamped to the bed The i present a downward incline in the direction of travel of the-slide and as the slide descends it Will turn the nut with the screw, thus decreasing the rate of travel of the tool relatively to the speed of rotation of the screw and eradicating a plus error.

When the device is adjusted, a cut is made and carefully gaged. Any error found can be corrected by manipulation of the block and the subsequent cuts necessary to coinplete the screw will remove the error from the finished article. I

lVhile I have described the'invention as applied to a lathe, it isobvious that it is equally applicable to thread grinders or thread milling machines. The tool support will, of course be provided with any tool suitable forthe machine to which the invention is applied.

Having now fully described my invention, what I claim and desire to protect by Letters Patent is: Y

1. A screw cutting lathe comprising a frame, a carriage adapted to be moved longitudinally on the frame, a lead screw, a 'nut on the lead screw connected to the carriage for moving the carriage, an auxiliary frame adjustably connected to the main frame, a plate adjustably'mounted 011 the auxiliary frame having a cam-way therein, means for locking the plate in its adjusted position, a block slidable in said cam-way, and a pivotal connection between said block and the nut.

2. A screw cutting lathe comprising a frame, a carriage adapted to be moved longitudinally on the frame, a lead screw, a nut on the lead screw connected tothe carriage for moving the carriage, an auxiliary frame adjustably connected to the main extending cam-way therein, said cam-way being of circular form, means for locking the plate in its adjusted position to the auxiliary frame, a cylindrical block in the cam-way arranged to slide and rotate therein, and a pivotal connection between the block and the nut. V

3. A screw cutting lathe comprising a frame, ways on the frame, a carriage mounted to slide onthe ways, a lead screw, a nut on the lead screw connected to the carriage to move the carriage, an auxiliary frame, said auxiliary frame having a recess for the reception of one of the ways, a clamp for adjustably securing the auxiliary frame on said way, a plate adjustably mounted on the auxiliary frame having a cam-way therein, means for locking the plate in its adjusted position, a slide mounted in the cam-way, and a driving'connection between the nut and the slide for moving the slide along the cam-way and for rotating the nut about the lead screw. 7

4. A screw cutting attachment for lathes, comprising a sleeve arranged to surround the'lead screw and adapted to be'attached to a lathe carriage, a lead screw nut associated withthe sleeve, a cam plate associated with the nut, a supporting frame on which the camplate is adjustably mounted, means for adjustably securing the cam plate to the frame, and a clamp for adjustably clamping the supporting frame to the ways of a lathe. V I

In testimony of which invention I have hereunto set myhand, at Gloucester City, N. J., on this 10th day of July, 1919.

FRANK H. DANIELS. 

